CN112822817B - Drive control circuit structure for realizing dimming function - Google Patents

Drive control circuit structure for realizing dimming function Download PDF

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CN112822817B
CN112822817B CN201911117865.5A CN201911117865A CN112822817B CN 112822817 B CN112822817 B CN 112822817B CN 201911117865 A CN201911117865 A CN 201911117865A CN 112822817 B CN112822817 B CN 112822817B
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CN112822817A (en
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刘玉芳
丁增伟
曾洁琼
张天舜
罗先才
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CRM ICBG Wuxi Co Ltd
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Abstract

The invention relates to a drive control circuit structure for realizing a dimming function, which comprises a duty ratio detection module, a pulse modulation module and a dimming control module, wherein the duty ratio detection module is used for sampling and calculating input pulse waves through a high-speed clock signal to obtain a group of digital output signals; the coding circuit module is used for generating a two-bit control signal through the digital output signal; the first digital-to-analog conversion circuit module is used for generating nonlinear change current and fixed current and further adjusting output current through a frequency modulation mode; a frequency modulation circuit module; the second digital-to-analog conversion circuit module is used for outputting voltage and further changing output current by changing peak voltage; a peak current detection circuit module; and a logic control circuit module. The driving control circuit structure for realizing the dimming function effectively improves the dimming precision and the dimming depth, can enable human eyes to feel light when being applied to the dimming and color-modulating occasions, can achieve softer change in both brightness and color tone, and can dim the brightness of a lamp at night.

Description

Drive control circuit structure for realizing dimming function
Technical Field
The invention relates to the field of smart homes, in particular to the field of LED dimming, and specifically relates to a driving control circuit structure for realizing a dimming function.
Background
The circuit structure of the prior art is shown in fig. 1, an alternating current input power supply is rectified by a rectifier bridge and then filtered by a capacitor C1 to generate a direct current power supply, a resistor R4 and a capacitor C5 generate a low-voltage signal VCC to start a driving chip, and an internal circuit of the driving chip clamps the VCC. After the circuit normally works, the power tube is conducted, and the primary side inductance N of the transformer T1 P The current rises gradually, the inductor stores energy, and the sampling resistor R CS Sampling the inductor current by a sampling resistor R CS When the voltage on the inductor reaches VREF, i.e. the inductor current I L Peak value to I PK ＝VREF/R CS The constant-current logic control circuit controls the power tube to be turned off, the voltage on the inductor to be reversed, and the inductor to be turned onAnd after the LED and D2 loops discharge, the voltage at two ends of the inductor drops when the inductor discharge is finished, when the zero-crossing detection circuit detects that the voltage of the ZCD pin drops, the zero-crossing detection circuit outputs a power tube starting signal to the constant-current logic control circuit, the power tube is started again, and the steps are repeated. When the PWM adjusts the light, when the PWM is high, the power loop of the circuit works, and when the PWM is low, the power loop of the circuit stops working.
Linear dimming changes the LED driving current by changing the peak current of the inductor by changing the voltage or resistance, but has the disadvantages that decreasing the peak current increases the operating frequency of the driving circuit, increases the switching loss, and decreases the LED current while causing the white light to shift to the yellow spectrum.
The PWM dimming method is a method of changing an output current by controlling a duty ratio of a PWM wave, and a power circuit of a circuit operates when the PWM is high, and stops operating when the PWM is low. When the frequency of the PWM dimming is 200 to 20kHz, the inductance and the output capacitance around the LED driver easily generate noise that can be heard by human ears. In addition, when PWM dimming is performed, the closer the frequency of the adjustment signal and the frequency of the gate control signal by the LED driving chip are, the worse the linearity effect is.
As shown in fig. 2, the duty ratio of the PWM1 signal is smaller than that of the PWM2 signal, but since the falling edge of PWM occurs at the demagnetization time, the magnitude of the output current is not changed. Affecting the accuracy of the dimming.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a driving control circuit structure which has high precision, simple structure and wider application range and realizes the dimming function.
In order to achieve the above object, the driving control circuit structure for realizing the dimming function of the present invention is as follows:
this realize drive control circuit structure of function of adjusting luminance, its key feature is, circuit structure include:
the duty ratio detection module is used for sampling and calculating input pulse waves through a high-speed clock signal to obtain a group of digital output signals;
the coding circuit module is connected with the duty ratio detection module and is used for generating a two-bit control signal through the digital output signal;
the first digital-to-analog conversion circuit module is connected with the duty ratio detection module and the coding circuit module and is used for generating nonlinear change current and fixed current so as to regulate output current through a frequency modulation mode;
the frequency modulation circuit module is connected with the first digital-to-analog conversion circuit module and used for generating a delay signal to enable the circuit to enter an intermittent working mode, and changing the duty ratio of a switch by changing the working frequency of a power tube so as to change the output current;
the second digital-to-analog conversion circuit module is connected with the duty ratio detection module and the coding circuit module and is used for outputting voltage and further changing output current by changing peak voltage;
the peak current detection circuit module is connected with the second digital-to-analog conversion circuit module and used for changing CS peak sampling voltage and changing output current by changing the peak current of the inductor;
and the logic control circuit module is connected with the frequency modulation circuit module and the peak current detection circuit module and is used for controlling the output current to carry out light source dimming.
Preferably, the first digital-to-analog conversion circuit module includes:
the fixed current generation circuit submodule is connected with the duty ratio detection module and is used for generating fixed current;
and the variable current generation circuit submodule is connected with the duty ratio detection module and is used for generating variable current.
Preferably, the fixed current generating circuit sub-module comprises:
the first negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current;
and the first P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating fixed charging current.
Preferably, the variable current generating circuit sub-module comprises:
the second negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current;
the second P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating mirror current;
and the N-tube current mirror circuit unit is connected with the first negative feedback circuit unit and the second P-tube current mirror circuit unit and is used for generating variable discharge current.
Preferably, the duty ratio detection module enables the first digital-to-analog conversion circuit module and the second digital-to-analog conversion circuit module to output different segmented analog signals by changing the code of the digital output signal.
Preferably, the second digital-to-analog conversion circuit module is an R-2R type digital-to-analog conversion circuit.
Preferably, the second digital-to-analog conversion circuit module obtains an output voltage, specifically:
the output voltage is obtained according to the following formula:
Figure BDA0002274587110000031
where VCS _ REF is the output voltage, V REF0 The full current corresponds to the sampling reference voltage.
Preferably, the frequency modulation circuit module generates a delay and obtains a delay time, specifically:
the delay time is obtained according to the following formula:
Figure BDA0002274587110000032
wherein, T DELAY For time delay, i.e. discharge time, T SW For the charging time, i.e. the switching period in critical conduction mode of the power transistor, I charge For charging current, I discharge To put inAn electrical current.
Preferably, the frequency modulation circuit module obtains an output current, specifically:
obtaining the output current I of the frequency modulation circuit module according to the following formula LED1 ：
Figure BDA0002274587110000041
Wherein, I LED0 100% of the output current, D1 is the proportion of the output current changed by the switch delay, T DELAY For time delay, i.e. discharge time, T SW The charging time is the switching period of the power tube in critical conduction mode.
Preferably, the peak current detection circuit module obtains an output current, specifically:
obtaining the output current I of the peak current detection circuit module according to the following formula LED2 ：
Figure BDA0002274587110000042
Wherein, I LED0 Is 100% of output current, V REF0 At full current, the reference voltage is sampled, D2 is the output current ratio adjusted by changing the reference voltage, and VCS _ REF is the output voltage.
By adopting the drive control circuit structure for realizing the dimming function, the output current of the LED is adjusted by adjusting the frequency modulation mode and changing the peak voltage, so that the dimming function effect of the LED is realized. The intelligent household dimming circuit can effectively improve dimming precision and dimming depth, can achieve a better dimming effect compared with the prior art, meets the high-quality dimming quality requirement of intelligent household, can solve the noise problem in dimming due to the fact that the current passing through the circuit structure is small, and has a wide application range.
Drawings
Fig. 1 is a diagram of a prior art dimming circuit.
Fig. 2 is a waveform diagram of the prior art.
Fig. 3 is a schematic diagram of a driving control circuit structure for implementing a dimming function according to the present invention.
FIG. 4 shows D1, D2 and I of the present invention LED F and PWM are shown as the change relation of the duty ratio.
Fig. 5 is a schematic circuit diagram of a second digital-to-analog conversion circuit module according to the present invention.
FIG. 6 is a diagram illustrating the variation curve of VCS _ REF according to the present invention.
Fig. 7 is a schematic circuit diagram of a first digital-to-analog conversion circuit module according to the present invention.
Fig. 8 is a schematic diagram of a digital-to-analog converter of the variable current generating circuit module according to the present invention.
Fig. 9 is a schematic circuit diagram of the resistor of the variable current generating circuit module according to the present invention.
FIG. 10 is a graphical representation of Idischarge/Icharge of the present invention as a function of duty cycle.
Fig. 11 is a block diagram of a frequency modulation circuit according to the present invention.
FIG. 12 shows D1, D2, I of another embodiment of the present invention LED F and PWM as a function of the duty cycle.
Fig. 13 is a schematic circuit diagram of a second digital-to-analog conversion circuit module according to another embodiment of the invention.
FIG. 14 is a diagram illustrating a variation curve of VCS _ REF according to another embodiment of the present invention.
Fig. 15 is a schematic diagram of a digital-to-analog converter of a variable current generating circuit module according to another embodiment of the invention.
Fig. 16 is a schematic circuit diagram of a resistor of a variable current generating circuit module according to another embodiment of the invention.
FIG. 17 is a graph of Idischarge/Icharge as a function of duty cycle for another embodiment of the present invention.
Detailed Description
In order that the technical contents of the present invention can be more clearly described, the present invention will be further described with reference to specific embodiments.
The driving control circuit structure for realizing the dimming function of the invention comprises:
the duty ratio detection module is used for sampling and calculating input pulse waves through a high-speed clock signal to obtain a group of digital output signals;
the coding circuit module is connected with the duty ratio detection module and is used for generating a two-bit control signal through the digital output signal;
the first digital-to-analog conversion circuit module is connected with the duty ratio detection module and the coding circuit module and is used for generating nonlinear change current and fixed current so as to regulate output current through a frequency modulation mode;
the frequency modulation circuit module is connected with the first digital-to-analog conversion circuit module and used for generating a delay signal to enable the circuit to enter an intermittent working mode, and changing the duty ratio of a switch by changing the working frequency of a power tube so as to change the output current;
the second digital-to-analog conversion circuit module is connected with the duty ratio detection module and the coding circuit module and is used for outputting voltage and further changing output current by changing peak voltage;
the peak current detection circuit module is connected with the second digital-to-analog conversion circuit module and used for changing CS peak sampling voltage and changing output current by changing the peak current of the inductor;
and the logic control circuit module is connected with the frequency modulation circuit module and the peak current detection circuit module and is used for controlling the output current to carry out light source dimming.
As a preferred embodiment of the present invention, the first digital-to-analog conversion circuit module includes:
the fixed current generation circuit submodule is connected with the duty ratio detection module and is used for generating fixed current;
and the variable current generation circuit submodule is connected with the duty ratio detection module and is used for generating variable current.
As a preferred embodiment of the present invention, the fixed current generating circuit sub-module comprises:
the first negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current;
and the first P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating fixed charging current.
As a preferred embodiment of the present invention, the variable current generation circuit sub-module comprises:
the second negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current;
the second P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating mirror current;
and the N-tube current mirror circuit unit is connected with the first negative feedback circuit unit and the second P-tube current mirror circuit unit and is used for generating variable discharge current.
As a preferred embodiment of the present invention, the duty ratio detection module changes the code of the digital output signal, so that the first digital-to-analog conversion circuit module and the second digital-to-analog conversion circuit module output different segmented analog signals.
In a preferred embodiment of the present invention, the second digital-to-analog conversion circuit module is an R-2R type digital-to-analog conversion circuit.
As a preferred embodiment of the present invention, the second digital-to-analog conversion circuit module obtains an output voltage, specifically:
the output voltage is obtained according to the following formula:
Figure BDA0002274587110000071
where VCS _ REF is the output voltage, V REF0 The full current corresponds to the sampling reference voltage.
As a preferred embodiment of the present invention, the frequency modulation circuit module generates a delay and obtains a delay time, specifically:
the delay time is obtained according to the following formula:
Figure BDA0002274587110000072
wherein, T DELAY For time delay, i.e. discharge time, T SW For the charging time, i.e. the switching period in critical conduction mode of the power transistor, I charge For charging current, I discharge Is a discharge current.
As a preferred embodiment of the present invention, the frequency modulation circuit module obtains an output current, specifically:
obtaining the output current I of the frequency modulation circuit module according to the following formula LED1 ：
Figure BDA0002274587110000073
Wherein, I LED0 100% of the output current, D1 is the proportion of the output current changed by the switch delay, T DELAY For time delay, i.e. discharge time, T SW The charging time is the switching period of the power tube in critical conduction mode.
As a preferred embodiment of the present invention, the peak current detection circuit module obtains an output current, specifically:
obtaining the output current I of the peak current detection circuit module according to the following formula LED2 ：
Figure BDA0002274587110000074
Wherein, I LED0 Is 100% of output current, V REF0 At full current, the sample reference voltage is used, D2 is the output current ratio adjusted by changing the reference voltage, and VCS _ REF is the output voltage.
In an embodiment of the present invention, a non-isolated driving dimming control circuit with excellent dimming effect is disclosed, and as shown in fig. 3, the driving dimming control circuit includes a duty ratio detection module, an encoding circuit module, a first digital-to-analog conversion circuit module, a frequency modulation circuit module, a second digital-to-analog conversion circuit module, a peak current detection circuit module, and a logic control circuit module.
The duty ratio detection module is connected with the coding circuit module, the first digital-to-analog conversion circuit module and the second digital-to-analog conversion circuit module, the coding circuit module is connected with the first digital-to-analog conversion circuit module and the second digital-to-analog conversion circuit module, the frequency modulation circuit module is connected with the first digital-to-analog conversion circuit module, the peak current detection circuit module is connected with the second digital-to-analog conversion circuit module, and the logic control circuit module is connected with the frequency modulation circuit module and the peak current detection circuit module.
The interface comprises a CS (Current sensor) interface, a GD (Gate Driver) interface, a ZCD (Zero Current Detect) interface, a Zero Current detection interface and a grid Driver interface, wherein the CS interface, the GD interface and the ZCD interface are interface names, the CS interface is an inductance peak Current detection port, the GD interface Driver interface drives an output port, and the ZCD interface is an inductance Zero Current detection port.
The duty ratio detection module samples and calculates input pulse waves through a high-speed clock signal to obtain a group of digital output signals, and the first digital-to-analog conversion circuit module and the second digital-to-analog conversion circuit module output different segmented analog signals by changing the codes of the digital output signals. The coding circuit module generates a two-bit control signal through a digital output signal, wherein the digital output signal has n bits and is D<n-1：0>The two-bit control signal is A 1 A 0 。
The circuit structure of the invention changes the output current of the LED in two different ways, and the technical scheme of the invention is further explained in detail by combining the attached drawings:
1. the first embodiment is as follows:
the first embodiment regulates the output current through a frequency modulation scheme. The digital output signal and the two-bit control signal control the first digital-to-analog conversion circuit module circuit to generate a nonlinear change current and a fixed current, and the current is output to the frequency modulation circuit to generate a delay signal. At the moment, the system enters an intermittent working mode, the duty ratio of a switch is changed by changing the working frequency of the power tube, the average current output by the LED is further changed, and the dimming function and effect of the LED are realized.
Taking the example of generating two-bit control signals by the encoding circuit, the duty ratio of the PWM signal is D, and the calculation formula of the duty ratio D is as follows:
D＝D1×D2；
wherein, D1 is the output current proportion changed by switching time delay, and D2 is the output current proportion regulated by changing reference voltage. D1, D2, I LED The relationship of the variation of f and the PWM duty ratio is shown in fig. 4.
1.1 coding circuit module:
the truth table of the coding circuit block is as follows, taking n =12 as an example:
PWM duty cycle D<11：0>(hexadecimal) A1A0
100％～50％ FFF～800 00
50％～12.5％ 7FF～200 01
12.5％～3.125％ 1FF～080 10
3.125％～0％ 07F～0 11
1.2 the first digital-to-analog conversion circuit module:
as shown in fig. 7, the first digital-to-analog conversion circuit module generates a non-linearly varying current and a fixed current, and then adjusts the output current through a frequency modulation mode. The first digital-to-analog conversion circuit module comprises a fixed current generation circuit submodule and a variable current generation circuit submodule which are connected with the duty ratio detection module.
The fixed current generation circuit submodule is used for generating fixed current and comprises a first negative feedback circuit unit consisting of operational amplifiers AMP1 and MN6 and a first P pipe current mirror circuit unit consisting of MP 5-MP 8. The input end of the first negative feedback circuit unit is connected with the duty ratio detection module, and the output end of the first negative feedback circuit unit is connected with the first P tube current mirror circuit unit and used for generating current; the first P-tube current mirror circuit unit is used for generating a fixed charging current.
The first negative feedback circuit unit enables the voltage of the inverting input end of the AMP1 to be equal to V1, the current flowing through R1 is V1/R1, and then the charging current Icharge is generated through the first P tube current mirror circuit unit.
The variable current generation circuit submodule is used for generating variable current and comprises a voltage digital-to-analog conversion circuit DAC1_1 and a resistor R2 which are R _ DAC, and further comprises a second negative feedback circuit unit consisting of an operational amplifier AMP2 and an operational amplifier MN1, a second P tube current mirror circuit unit consisting of MP1 to MP4, and an N tube current mirror circuit unit consisting of MN2 to MN 5.
The second negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current; the second P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating mirror current; and the N-tube current mirror circuit unit is connected with the first negative feedback circuit unit and the second P-tube current mirror circuit unit and is used for generating variable discharge current.
The second negative feedback circuit unit enables the voltage of the inverting input end of the operational amplifier AMP2 to be equal to V2, the current flowing through R2 is V2/R2, and then the discharge current Idischarge is generated through the second P tube current mirror circuit unit and the N tube current mirror circuit unit.
The internal circuit structure of the voltage digital-to-analog conversion circuit DAC1_1 is shown in fig. 8, the voltage digital-to-analog conversion circuit structure is shown in fig. 5, the number of bits is one bit less, and the output signals of the data selector and V2 change as follows:
when A1A0 is 00, y <10:0> = d0<10:0> =111 1111, V2= V1;
when A1A0 is 01, y<10：0>＝d1<10：0>＝D<10：0>V2 with D<10：0>The change is a linear change in the direction of the linear change,
Figure BDA0002274587110000101
when A1A0 is 10, y <10:0> = d2<10:0> =010 0000 0000, V2= V1/4;
when A1A0 is 11, y<10：0>＝d3<10：0>＝{D<8：0>00}, V2 with D<10：0>The change in the shape of a line is linear,
Figure BDA0002274587110000102
the internal circuit configuration of the resistor R2, i.e., R _ DAC, is shown in fig. 9, the output signal of the data selector and the change of the resistor R2 are as follows, as shown in fig. 8:
when A1A0 is 00, y <10:0> = d0<10:0> =111 1111, R2= R/16;
when A1A0 is 01, y<10：0>＝d1<10：0>＝D<10：0>，
Figure BDA0002274587110000103
Figure BDA0002274587110000104
The range is R/16-96R, and the stepping is R/16;
when A1A0 is 10, y <10:0> = d2<10:0> =010 0000 0000, R2=96R;
when A1A0 is 11, y<10：0>＝d3<10：0>＝{D<8：0>，00}，
Figure BDA0002274587110000105
Figure BDA0002274587110000106
The range is 96R to 128R, and the step is R/4.
Referring to fig. 7 to 9, the fixed current Icharge = V1/R1, the variable current Idischarge = V2/R2, R1=128r, and the duty ratio-dependent curves of Idischarge/Icharge are shown in fig. 10.
1.3 frequency modulation circuit module:
as shown in fig. 11, the frequency modulation circuit module generates a delay signal to make the circuit enter an intermittent operation mode, and changes the duty ratio of the switch by changing the operating frequency of the power transistor, thereby changing the output current.
The power tube is started, the capacitor C1 is charged by the charging current Icharge, and the capacitor C1 is discharged by the discharging current Idischarge after demagnetization is finished. The charging time is the switching period of the power tube in the critical conduction mode and is recorded as T SW The delay of the discharge time for increasing, denoted as T DELAY 。
The frequency modulation circuit module generates time delay, and obtains the time delay time according to the following formula:
Figure BDA0002274587110000111
wherein, T DELAY For time delay, i.e. discharge time, T SW For the charging time, i.e. the switching period in critical conduction mode of the power transistor, I charge For charging current, I discharge Is a discharge current.
The frequency modulation circuit module obtains an output current I according to the following formula LED1 ：
Figure BDA0002274587110000112
Wherein, I LED0 100% of the output current, D1 is the proportion of the output current changed by the switch delay, T DELAY To delay time, i.e. discharge time, T SW The charging time is the switching period of the critical conduction mode of the power tube.
The first starting signal of the power tube output by the logic control circuit is a START signal, the starting signal of the power tube output by the logic control circuit after the first starting is DRV _ H, and the demagnetization finishing signal output by the zero-crossing detection circuit is ZCD _ IN.
When A1A0 is 00, D1=1,
Figure BDA0002274587110000113
when A1A0 is 01,
Figure BDA0002274587110000114
Figure BDA0002274587110000115
Figure BDA0002274587110000116
when A1A0 is 10, the composition,
Figure BDA0002274587110000117
when A1A0 is 11,
Figure BDA0002274587110000121
Figure BDA0002274587110000122
Figure BDA0002274587110000123
1.4 second digital-to-analog conversion circuit module:
as shown in fig. 5, the second digital-to-analog conversion circuit module is used for outputting voltage, and further changing output current by changing peak voltage. The second digital-to-analog conversion circuit module is an R-2R type digital-to-analog conversion circuit, bi =1, and the switch is connected to V REF0 Bi =0, the switch is connected to GND.
The second digital-to-analog conversion circuit module obtains an output voltage according to the following formula:
Figure BDA0002274587110000124
where VCS _ REF is the output voltage, V REF0 The full current corresponds to the sampling reference voltage.
The second digital-to-analog conversion circuit module comprises a 1-out-of-4 data selector, and the output of the data selector and the change of the VCS _ REF value are as follows:
a1A0=00, y<11：0>＝d0<11：0>＝D<11：0>VCS _ REF with D<11：0>From V REF0 Linearly decreasing to V REF0 /2，
Figure BDA0002274587110000125
When A1A0=01, y<11：0>＝d1<11：0>＝1000 0000 0000，VCS_REF＝V REF0 /2；
A1A0=10, y<11：0>＝d2<11：0>＝{D<9：0>00}, VCS _ REF with D<11：0>From V REF0 Linearly decreasing to V REF0 /8，
Figure BDA0002274587110000126
A1A0=11, y<11：0>＝d3<11：0>＝0010 0000 0000，VCS_REF＝V REF0 /8
The variation curve of VCS _ REF is shown in fig. 6.
In summary, the digital output signal of the first embodiment of the present invention is converted into the delay control signal through the first digital-to-analog conversion circuit module by the encoding circuit module, and is converted into the CS sampling peak voltage signal through the second digital-to-analog conversion circuit module, so as to control the output current variation of the LED in a segmented manner. According to the embodiment of the invention, the duty ratio of the switch is changed by changing the working frequency of the power tube, so that the average current output by the LED is changed, and the dimming function effect of the LED is realized.
The calculation formula of the output current after the time delay is increased is as follows:
Figure BDA0002274587110000131
the calculation formula of the power tube frequency is as follows:
Figure BDA0002274587110000132
wherein, I LED0 Is 100% of output current, f 0 100% of the operating frequency of the switch, D1 the proportion of the output current which is varied by the switching delay, T SW The time from the turn-on of the power tube to the end of demagnetization, T DELAY For increased switching delay.
2. The second embodiment:
embodiments regulate the output current by peak voltage. The digital signal output controls a second digital-to-analog conversion circuit module circuit to change CS peak sampling voltage, and the LED output current is changed by changing the peak current of the inductor, so that the dimming function effect of the LED is realized. Wherein, D1, D2 and I LED The relationship of variation of f and the PWM duty ratio is shown in fig. 12.
2.1 coding circuit module:
the truth table of the coding circuit block is as follows, taking n =12 as an example:
PWM duty cycle D<11：0>(hexadecimal) A1A0
100％～50％ FFF～800 00
50％～12.5％ 7FF～200 01
12.5％～6.25％ 1FF～100 10
6.25％～0％ 0FF～0 11
2.2 the first digital-to-analog conversion circuit module:
fig. 15 is a schematic diagram of the voltage digital-to-analog conversion circuit DAC1_1 in the internal circuit of the first digital-to-analog conversion circuit module.
Compared with the first digital-to-analog conversion circuit block in the first embodiment, because the input signals of the data selectors are different, the output signals of the data selectors and V2 are also different, and the output signals of the data selectors and V2 are changed as follows:
when A1A0 is 00, y <10:0> = d0<10:0> =111 1111, V2= V1;
when A1A0 is 01, y <10:0> = d1<10:0> =100 0000 0000, V2= V1/2;
when A1A0 is 10, y <10:0> = d2<10:0> =010 0000 0000, V2= V1/4;
A1A0 is 11When y is<10：0>＝d3<10：0>＝{D<8：0>00, V2 with D<10：0>The change in the shape of a line is linear,
Figure BDA0002274587110000141
fig. 16 shows an internal circuit of the resistor R2, i.e., R _ DAC, and compared with the resistors in the first embodiment, the input signal of the data selector is different, the output signal of the data selector is also different from the resistor R2, and the output signal of the data selector and the resistor R2 are changed as follows:
when A1A0 is 00, y <10:0> = d0<10:0> =111 1111, R2= R/16;
when A1A0 is 01, y <10:0> = d1<10:0> =100 0000 0000, R2=64R;
when A1A0 is 10, y <10:0> = d2<10:0> =010 0000 0000, R2=96R;
when A1A0 is 11, y<10：0>＝d3<10：0>＝{D<8：0>，00}，
Figure BDA0002274587110000142
Figure BDA0002274587110000143
The range is 96R to 128R, and the step is R/4.
Referring to fig. 15 and 16, the fixed current is Icharge = V1/R1, the variable current is Idischarge = V2/R2, R1=128r, and the duty cycle variation curve of Idischarge/Icharge is shown in fig. 17.
2.3 second digital-to-analog conversion circuit module:
as shown in fig. 13, the second digital-to-analog conversion circuit module includes a 1-out-of-4 data selector, and the input signal of the data selector in this embodiment is different from that in the first embodiment.
As shown in fig. 14, the output of the data selector and the change in VCS _ REF value are as follows:
when A1A0 is 00, y<11：0>＝d0<11：0>＝D<11：0>VCS _ REF with D<11：0>From V REF0 Linearly decreasing to V REF0 /2，
Figure BDA0002274587110000144
When A1A0 is 01, y<11：0>＝d1<11：0>＝{D<10：0>0, VCS _ REF with D<10：0>From V REF0 Linearly decreasing to V REF0 /4，
Figure BDA0002274587110000145
When A1A0 is 10, y<11：0>＝d2<11：0>＝{D<9：0>00, VCS _ REF with D<11：0>From V REF0 Linearly decreasing to V REF0 /4，
Figure BDA0002274587110000146
When A1A0 is 11, y<11：0>＝d3<11：0>＝0010 0000 0000，VCS_REF＝V REF0 /4。
2.4 peak current detection circuit module:
the peak current detection circuit module changes the CS peak sampling voltage and changes the output current by changing the peak current of the inductor.
The peak current detection circuit module obtains an output current I according to the following formula LED2 ：
Figure BDA0002274587110000151
Wherein, I LED0 Is 100% of output current, V REF0 At full current, the sample reference voltage is used, D2 is the output current ratio adjusted by changing the reference voltage, and VCS _ REF is the output voltage.
2.4 logic control circuit module:
the logic control circuit module is used for controlling the output current to carry out light source dimming.
In summary, in the embodiment of the invention, the CS peak sampling voltage is changed, and the peak current of the inductor is changed to further change the output current of the LED, so as to achieve the dimming function effect of the LED.
The calculation formula of the output current is as follows:
Figure BDA0002274587110000152
the calculation formula of the power tube frequency is as follows:
Figure BDA0002274587110000153
wherein, V REF0 For full current corresponding to the sampled reference voltage, D2 is the proportion of the output current regulated by varying the reference voltage, I LED0 Is 100% of output current, f 0 The switching frequency is 100%, and VCS _ REF is the output voltage.
By adopting the drive control circuit structure for realizing the dimming function, the output current of the LED is adjusted by adjusting the frequency modulation mode and changing the peak voltage, so that the dimming function effect of the LED is realized. The invention can effectively improve the dimming precision and the dimming depth, can achieve better dimming effect compared with the prior art, and meets the high-quality dimming quality requirement of the smart home. And because the current that passes in the circuit structure is less, the invention can solve the noise problem while dimming too, have extensive application range.
In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims (10)

1. A drive control circuit structure for realizing dimming function is characterized in that the circuit structure comprises:
the duty ratio detection module is used for sampling and calculating input pulse waves through a high-speed clock signal to obtain a group of digital output signals;
the coding circuit module is connected with the duty ratio detection module and is used for generating a two-bit control signal through the digital output signal;
the first digital-to-analog conversion circuit module is connected with the duty ratio detection module and the coding circuit module and is used for generating nonlinear change current and fixed current and further regulating output current through a frequency modulation mode;
the frequency modulation circuit module is connected with the first digital-to-analog conversion circuit module and used for generating a delay signal to enable the circuit to enter an intermittent working mode, and changing the duty ratio of a switch by changing the working frequency of a power tube so as to change the output current;
the second digital-to-analog conversion circuit module is connected with the duty ratio detection module and the coding circuit module and is used for outputting voltage and further changing output current by changing peak voltage;
the peak current detection circuit module is connected with the second digital-to-analog conversion circuit module and is used for changing CS peak sampling voltage, namely peak sampling voltage of an inductor peak current detection port and changing output current by changing peak current of an inductor;
and the logic control circuit module is connected with the frequency modulation circuit module and the peak current detection circuit module and is used for controlling the output current to carry out light source dimming.
2. The structure of claim 1, wherein the first digital-to-analog conversion circuit module comprises:
the fixed current generation circuit submodule is connected with the duty ratio detection module and is used for generating fixed current;
and the variable current generation circuit submodule is connected with the duty ratio detection module and is used for generating variable current.
3. The driving control circuit structure for implementing dimming function as claimed in claim 2, wherein the fixed current generating circuit sub-module comprises:
the first negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current;
and the first P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating fixed charging current.
4. The driving control circuit structure for implementing dimming function as claimed in claim 3, wherein the variable current generating circuit sub-module comprises:
the second negative feedback circuit unit is connected with the duty ratio detection module and is used for generating current;
the second P tube current mirror circuit unit is connected with the first negative feedback circuit unit and is used for generating mirror current;
and the N-tube current mirror circuit unit is connected with the first negative feedback circuit unit and the second P-tube current mirror circuit unit and is used for generating variable discharge current.
5. The structure of claim 1, wherein the duty ratio detection module changes the code of the digital output signal to enable the first digital-to-analog conversion circuit module and the second digital-to-analog conversion circuit module to output different segmented analog signals.
6. The structure of claim 1, wherein the second digital-to-analog conversion circuit module is an R-2R type digital-to-analog conversion circuit.
7. The driving control circuit structure for realizing a dimming function according to claim 1, wherein the second digital-to-analog conversion circuit module obtains an output voltage, specifically:
the output voltage is obtained according to the following formula:
Figure FDA0003833980140000021
where VCS _ REF is the output voltage, V REF0 Corresponding to the sampling reference voltage at full current, n is the digit of the digital-to-analog conversion circuit, b i Is the value of the ith bit of a 12-bit binary input, i is an integer ranging from 0 to n-1.
8. The driving control circuit structure for realizing a dimming function according to claim 1, wherein the frequency modulation circuit module generates a delay time and obtains a delay time, specifically:
the delay time is obtained according to the following formula:
Figure FDA0003833980140000022
wherein, T DELAY For time delay, i.e. discharge time, T SW For the charging time, i.e. the switching period in critical conduction mode of the power transistor, I charge For charging current, I discharge Is a discharge current.
9. The driving control circuit structure for realizing a dimming function according to claim 1, wherein the frequency modulation circuit module obtains an output current, specifically:
obtaining the output current I of the frequency modulation circuit module according to the following formula LED1 ：
Figure FDA0003833980140000023
Wherein, I LED0 100% of the output current, D1 is the proportion of the output current changed by the switch delay, T DELAY For time delay, i.e. discharge time, T SW The charging time is the switching period of the critical conduction mode of the power tube.
10. The driving control circuit structure for realizing a dimming function according to claim 1, wherein the peak current detection circuit module obtains an output current, specifically:
obtaining the output current I of the peak current detection circuit module according to the following formula LED2 ：
Figure FDA0003833980140000031
Wherein, I LED0 Is 100% of output current, V REF0 At full current, the reference voltage is sampled, D2 is the output current ratio adjusted by changing the reference voltage, and VCS _ REF is the output voltage.
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